| Pin | Name | Description | 
  
    | 1 | GND | Digital ground | 
  
    | 2 | MIC/JCONN | External audio input from accessories or handsfree microphone. Multiplexed with junction box connection control signal | 
  
    | 3 | AGND | Analogue ground for accessories | 
  
    | 4 | TDA | Transmitted DBUS data to the accessories | 
  
    | 5 | M2BUS | Serial Bidirectional data and control between the handportable and accessories | 
  
    | 6 | HOOK/RXD2 | Hook indication. HP has a 100KE pull-up resistor | 
  
    | 7 | PHFS/TXD2 | Handsfree device power on/off, data to flash programming device | 
  
    | 8 | VCHAR | Battery charging voltage | 
  
    | 9 | GND | Digital ground | 
  
    | 10 | EAR/HFPWR | External Audio output to accessories or handsfree speaker | 
  
    | 11 | DSYNC | DBUS data bit sync clock | 
  
    | 12 | RDA | DBUS recieved data from the accessories | 
  
    | 13 | BENA | Power supply to headset adapter | 
  
    | 14 | VF | Programming voltage for FLASH | 
  
    | 15 | DCLK | DBUS data clock | 
  
    | 16 | VCHAR | Battery charging voltage |